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SSB demod, was Re: carrirer oscillator

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  • jabauzit
    ... the ... 1/F, ... performance. ... Hello Bob, Could you resume in a few sentences the difference between the SoftRock-40 and the SDR-1000 in this regard? I
    Message 1 of 31 , Oct 1, 2005
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      --- In softrock40@yahoogroups.com, Robert McGwier <rwmcgwier@c...>
      wrote:
      > This is not what we do on the Softrock40. The 11 kHz IF is used in
      the
      > SDR-1000 in order to do exactly what Frank says and that is avoid
      1/F,
      > DC, junk, noise, etc. at 0. We are attempting to maximize the
      performance.
      >

      Hello Bob,

      Could you resume in a few sentences the difference between the
      SoftRock-40 and the SDR-1000 in this regard?
      I could go back to the articles on the SDR-1000 and try to figure it
      out, but I think that you can give a better answer.

      The softRock-40 has a fixed oscillator and can software-tune +/- 24
      kHz around that frequency which means that near the oscillator
      frequency we get "junk". With the SDR-1000 what happens when we tune
      a particular frequency?

      Jean-Claude Abauzit, PJ2BVU
    • Bill Tracey
      When tuning an SDR 1000, if spur reduction is turned off, the DDS is tuner 11025 khz below the frequency of interest and the software (DttSP) oscillator is set
      Message 31 of 31 , Oct 1, 2005
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        When tuning an SDR 1000, if spur reduction is turned off, the DDS is tuner
        11025 khz below the frequency of interest and the software (DttSP)
        oscillator is set to -11025 khz to recover the frequency of interest. This
        works well but for the spurs from the DDS.

        If spur reduction is turned on (the normal case) the DDS is tuned to the
        nearest low spur point (as documented by some of the AD docs) and then
        DttSP oscillator is set to an appropriate value to recover the signal of
        interest. This generally results in a DttSP oscillator value between -9.5
        and -12.5 khz.

        On the SoftRock all the tuning is done with the DttSP oscillator and it
        ranges over +/- 24 khz - giving a tuning range of 48 khz.

        Regards,

        Bill (kd5tfd)
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